Laser technology laser spatial coherence affects illumination uniformity.
Is the mutual function of the light wave field u(r, t).
It can be known that the intensity of a point Q in the two-beam interference pattern is: laser technology A2, A3), transmitted to the receiving screen through the atmosphere, and then the illumination spot on the screen is recorded by a CCD camera. In the experiment, there are vegetation under the beam transmission path, the beam is about 1m~20m from the ground, and the transmission distance is 800m. Under the three states of the light source, 20 images are collected on the illumination target plane.
According to the definition of equation (2), the light intensity flicker rate can be calculated from the collected illumination spot pattern. The calculation method is as follows: first, read the light intensity y') at any point of the illumination spot, and then calculate the intensity of the illumination spot by (2): The upper N is the number of samples. It is a curve of the light intensity flickering rate with time in three states of the source laser beam. As can be seen from the figure, when the light source is in the Aj state (V = 0.5), the light intensity flicker rate is large, and fluctuates around 0.3 with time; when the light source is in the A2 state (F = 0.43), the light intensity flicker rate Decreased and fluctuated around 0.2 with time; when the light source was in the A3 state (V = 0.37), the light intensity flicker rate was the smallest and fluctuated around 0.1 with time. Obviously, the flicker rate is closely related to the spatial coherence of the illumination source beam. When the spatial coherence of the light source beam is poor, the scintillation rate is small and the uniformity of the illumination spot is good.
It is a curve of the power spectral density (PSD) distribution of the illumination spot intensity under three states of the source laser beam. In order to reduce the influence of random factors on the power spectrum distribution of the intensity fluctuation, the Welch method is used for the average smoothing process. As can be seen from the figure, the illumination intensity spectrum density (PSD) is closely related to the source beam coherence. When the spatial coherence of the light source beam is good (V = 0.37), the PSD is also reduced in turn, indicating that the uniformity of the illumination spot is also better; this is consistent with the change of the flicker rate and the coherence of the source beam.
The results of the three experiments show that the spatial coherence of the illumination laser beam is closely related to the illumination uniformity. When the spatial coherence of the laser beam decreases, the intensity of the illumination spot on the target plane will decrease. The intensity spectrum intensity of the illumination intensity is also reduced, which indicates that the illumination uniformity is improved. Therefore, for laser illuminators, selecting multiple lasers with poor spatial coherence is more advantageous for illumination uniformity.
In this paper, only the experimental preliminary discussion and analysis of the influence of spatial coherence of illumination laser beam on illumination uniformity is carried out. In practical work, there are many factors affecting illumination uniformity, such as laser beam quality and emission. The system and the illumination source are in a variety of factors, such as focusing or diverging, and the process involved is more complicated and worthy of further research.
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